#include <iostream>

using namespace std;

int main()
{
    double n;
    cin >> n;
    double l = -100, r = 100;
    while (r - l > 1e-8)
    {
        double mid = (l + r) / 2;
        if (mid * mid * mid >= n)
        {
            r = mid;
        }
        else 
        {
            l = mid;
        }
    }
    printf("%.6lf\n", l);
    return 0;
}